What's involved in making an exhaust?

[skotl]

I'm an active member of a 4x4 forum and a lot of people talk about straight through and side-exit exhausts and it got me thinking; what exactly is involved in making an exhaust?

Assuming we're talking about 2.5" tube, is it (simply) a tube bender and some exhaust paste?
I'm guessing not, hence the question.

Ta
Scott

 

[zardoz]

Depends whether or not you want to bend your own, or you may buy pre formed bends, of all shapes and sizes, then weld them up. You can buy pre made manifolds or make your own. As for bending. You can bend your own, but manipulating pipes or tubes is not as easy as bending any flat bar, as it will crinkle or crumple if you dont use the correct formers, mandrels etc. (You can also pack with sand and bend with heat, but i know little or nothing about this.)

I also would not personally consider welding them unless I had a TIG. For that sort of thing I prefer the slower speed, and finer control a TIG can give you.

If you make a lot of them you can buy bend kits that allow you to mock up the exhaust on a vehicle, before you commit to purchasing and cutting pipe. But these are not cheap.

 

[BrokenBiker]

if its your first time, and likely to be the only one you do I would by pre-fromed bits and slot them all together, or look for an aftermarket exhaust that will simply bolt on.

I made an exhaust system for my dads bike and tried doing the bends with lobster back templates and a roller...it didn't work and I ended up buying preformed bends and welding them onto the pipe.

used mig to weld them, lowest settings possible to get full penetration so I could take my time and have a bit more control, although I do agree that TIG is probably the better option for it, especially with stainless exhausts

 

[AndyStobbs]

I'm on with making some manifolds for my v6. I bought a kit in mild steel first which had pre formed bends and made my mistakes with that. Now I'm about to start reconstructing it in 304 stainless. I am trying to avoid shelling out for pre formed bends at the moment and trialling ways of bending tube myself. If I make any good progress I will post it up.

 

[Llama]

Stainless looks pretty but tends to sound much worse in my opinion

 

[gulf]

stainless sounds tinny and its a bitch to bend in any easy way,if you get pre formed bends and universal hangers its a doddle.you can even buy exhaust pipe expanders which create a flared joint that you can clamp together.I have a set,but not overly impressed with them,im thinking its the brand i got as Ive seen others similar doing a good job.

 

[AndyStobbs]

stainless sounds tinny and its a bitch to bend in any easy way,if you get pre formed bends and universal hangers its a doddle.you can even buy exhaust pipe expanders which create a flared joint that you can clamp together.I have a set,but not overly impressed with them,im thinking its the brand i got as Ive seen others similar doing a good job.

I was lent a bergen set, they were useless even on mild steel.

thicker wall would combat the tinny sound of stainless.

 

[norlander]

I doubt this will be much use as its the kit used on V twin bikes
http://www.wwag.com/cgi-bin/WebObjects/WebSite.woa/wa/DirectAction?page=!32694
but there is a UK company called Demon Tweeks who may do something similar in the four wheel line.
I take it you intend using a silencer or inline baffles? I know nowt about cars, but on bikes, straight thru pipes can kill low to mid range torque, and can also cause the engine to run lean.
Many people equate louder exhausts with extra power but a dyno run often says different.
The hotrod/custom car lads on here are better qualified than me on 4wheel stuff though.

 

[hareng]

Done three using axle stands at rear, theyre not really worth the effort if you haven't a ramp. Spend more time trial fitting, tacking and removing building it up as you go along.

Best boxes ever had were Jetex. Can buy bends and butcher to suit have a look for any local proper exhaust fabricators that sell bends.
Round here theres Ashley in Walsall, bit further away where had everything from in last build V6 turbo inc Perkins down pipe from my old mate at Custom Chrome in Nuneaton.
http://www.custom-chrome.co.uk/retailshop.html Prices look dear to me.

 

[normspanners]

I am trying to avoid shelling out for pre formed bends at the moment and trialling ways of bending tube myself. If I make any good progress I will post it up.

Hi Andy a mate of mine makes stainless exhaust pipes for morgans, so when fitted are in your face and need to be perfect he bends them by filling them with water in a tall freezer and freezes them, then bends them absolutely perfectly no creases etc.

 

[AndyStobbs]

Thanks Norm. I saw that video of yoshimura that was posted recently, he seemed to make a nice job with just the flame. I tried that a day or two ago and kinked the pipe - it wasn't a big shock.
I thought I might try sand next if I can't suss out the heat bending.
Would have to beg/steal/borrow a freezer that big.

I'm slowly working toward a rotary draw bender, with internal mandrel. I have my eye on a basic frame work which has been designed for something else but is now redundant, that in itself is half way there already. I've now got a lathe for making my own formers, its probably only £500 short of being done in cost terms, but a good few hours of labour, and that is what I'm short of.

 

[chevy2]

Hi Andy a mate of mine makes stainless exhaust pipes for morgans, so when fitted are in your face and need to be perfect he bends them by filling them with water in a tall freezer and freezes them, then bends them absolutely perfectly no creases etc.

Wow, thats thinking outside the box,
Would never have thought to freeze pipe before bending it?.

My tube bender will bend stainless tube but i'd dont usually bother when building a full exhaust,
I'd rather buy the preformed bends and straight tube,
the bends will be a far tighter radius than what most tube benders are capable of which can help a lot for building some exhausts.

 

[piman]

Hello Andy,

as a matter of interest a well respected exhaust manifold designer is of the opinion that mild steel makes a better manifold than stainless from a performance point of view due to it's better thermal conductivity.

I have started making a manifold for my Jaguar and decided to try sand bending. There was a bit of work entailed in making a holder for the tube (I decided to do opposite hands of the manifold together, i.e two at a time so I could control the length to get them to match) with a jacking system to pack the sand tightly.

Initially I found that just jacking the sand didn't pack it properly and the tube kinked but subsequent tries jacking and tapping the tube was more successful and that is the key to getting good bends. I used a heating nozzle on my Oxy/acetylne torch and found that the tube heats up fairly quickly and then is easy to bend with an extension pipe as extra leverage.
Certainly a procedure that requires practice but good results can be had with this method.

Alec

 

[langy]

Wow, thats thinking outside the box,
Would never have thought to freeze pipe before bending it?.

My tube bender will bend stainless tube but i'd dont usually bother when building a full exhaust,
I'd rather buy the preformed bends and straight tube,
the bends will be a far tighter radius than what most tube benders are capable of which can help a lot for building some exhausts.

x 2

 

[outofthefire]

Initially I found that just jacking the sand didn't pack it properly and the tube kinked but subsequent tries jacking and tapping the tube was more successful and that is the key to getting good bends. I used a heating nozzle on my Oxy/acetylne torch and found that the tube heats up fairly quickly and then is easy to bend with an extension pipe as extra leverage.
Alec

Did you use bone dry silver sand? if not give it a go, it settles just by tapping the tube.

Something I am going to try sometime instead of sand is steel shot. I get loads of it for free from work and if it works wont need drying before using.

 

[norlander]

Wow, thats thinking outside the box,
Would never have thought to freeze pipe before bending it?.

http://www.youtube.com/watch?v=HQH0PYPeCTQ elf n safety and tidy workshop afficionados look away.

 

[piman]

Hello Out of the fire,

the sand (builders sand) was bone dry but what is silver sand?

Alec

 

[CompoSimmonite]

I need a full exhaust system for my Mahindra MM540 as it's completely missing from the manifold backwards.
I'm going to make a pattern out of standard plumbing waste fittings and then take to an exhaust fabricator (there is one near to me) and get them to bend on their CNC machine.

Paul H

 

[Shox Dr]

Hello Out of the fire,

the sand (builders sand) was bone dry but what is silver sand?

Alec

AKA Kiln Sand, also Patio sand or paving sand. It's been kin dried and sived.

Do a search on a WS8 or Cerabend, both on here and your favourite search engine

 

[outofthefire]

AKA Kiln Sand, also Patio sand or paving sand. It's been kin dried and sived.

Its also used in egg timers, its really fine so it flows like water when its dry. You buy it at builders merchants, its loads easier to use than builders sand. If you keep it outside in an unsealed container it absorbs moisture really quickly and needs drying in an oven.